By Kathleen Kodish Reeder

For decades the water quality of the Monongahela River and its tributaries in Pennsylvania has been impacted by the vast amount of coal mining in the region. One of the areas affected by this legacy is Friendship Hill National Historic Site (NHS) near Point Marion, Pennsylvania. An abandoned drift mine in the southeast corner of the park has been the discharge location for acidic water generated by oxidation of pyrite in the abandoned mine workings. This drainage has severely polluted Ice Pond Run, which flows through the park for almost 2 miles. Only species of invertebrates and plants that are tolerant of acid mine drainage can survive in the highly acidic environment. Although resolving this resource management problem has been a high priority throughout the past decade, until this year a feasible solution has been elusive.

Fortunately, a resourceful partnership that integrates the work of scientists from several organizations has brought new hope for the reclamation of Ice Pond Run. The partners include the National Park Service; the U.S. Geological Survey Biological Resources Division (USGS/BRD) Leetown Science Center (Kearneysville, West Virginia); the Conservation Fund’s Freshwater Institute; the Pennsylvania Department of Environmental Protection; and California University of Pennsylvania. In July 2000 the partners began diverting up to 60 gallons per minute of flow in Ice Pond Run for treatment at a facility using a process recently developed by the USGS. Funding for this research—which is the first full-scale application of the new process—has been contributed primarily by the USGS Natural Resources Preservation Program. Additional funding was provided by a generous grant from Canon U.S.A., Inc., through the National Park Foundation.

The innovative treatment process comprises eight distinct phases, but at the heart of the technology are four pulsed-bed limestone reactors. After the acid mine drainage has been saturated with carbon dioxide, pumps alternately force it to flow between two pairs of limestone columns in a pulsed cycle of 60 seconds. The highly acidic water comes into contact with a form of limestone commonly referred to as “glass sand.” At most sites using conventional fixed-bed reactors, a process called armoring (formation of an impervious coating) prevents limestone from being dissolved. However, the fluidization that results from using pulsed-bed reactors creates a highly energized environment where particle abrasion hinders armoring. The high quantities of free carbon dioxide and limestone then buffer the water’s pH, an essential step in the mitigation process.

Attempting to use this active treatment strategy in a remote location created several challenges. Perhaps the best evidence of the partners’ resourcefulness is the manner in which they addressed the problem of supplying one of the process’s chemical ingredients. The experimental treatment system in some cases requires bulk liquid carbon dioxide, which is expensive. However, neutralizing the acid with limestone produces high quantities of carbon dioxide within the reactors because the acidity of the acid mine drainage at Friendship Hill is extremely high. By modifying the system, researchers have been able to strip excess carbon dioxide from the water and recycle it at a rate that eliminates the need to purchase the chemical from outside sources. In fact, this facility is capable of capturing and reusing about 70,000 pounds of carbon dioxide per year. Additional carbon dioxide is available, when needed, in the exhaust from an on-site propane-powered electrical generator.

In terms of this research facility’s early performance, from July through September 2000 the plant had already processed 3.3 million gallons of acid mine drainage, consumed 30,000 pounds of limestone in its reactors, and removed 250,000 pounds of wet sludge (metal hydroxide precipitates). Over a three-year period the partners will monitor the effects of the treatment on water quality, aquatic macroinvertebrates, and fish. Those results will be compared with the characteristics of a reference stream (Dublin Run). As the operation and monitoring of the treatment plant proceed, the National Park Service welcomes scientific investigators, educators, and students to take advantage of the unique opportunities to study and teach others about this ecosystem and the detrimental effects of acid mine drainage.

Of course, reclaiming Ice Pond Run is just the first goal of the partners who have constructed this demonstration facility. In southwestern Pennsylvania alone, three of the four units in the National Park Service supervised by Superintendent Joanne Hanley are affected by acid mine drainage. As she has observed, “With this important research project, we can monitor the new treatment technology developed by the U.S. Geological Survey and determine its effectiveness in restoring good water quality and biological diversity to severely polluted park water resources.” Because the National Park Service protects and restores the quality of all surface and ground waters, the application of the pulsed-limestone technology at Friendship Hill National Historic Site has clearly assumed national importance.